To machine a work by a machine tool, a plurality of tools are attached to a turret type or comb-tooth type tool rest, and assigning a tool suitable for machining the work to a machining position. Then, the machining is carried out by rotating a spindle or the tool gripping the work or the like, and pressing the tool to the work.
Especially, in a numerical control (NC) machine tool for automatically carrying out a series of machining steps, the tool is attached through a tool holder to the tool rest. If necessary, the tool can be easily exchanged together with the tool holder.
One of such tool holders is disclosed in, for example, Japanese Patent No. 2878690, which can attach a plurality of tools to a holder body.
FIGS. 16(a) to 16(c) are explanatory views each showing a work machining method by an NC lathe described in Japanese Patent No. 2878690 mentioned above.
The NC lathe described therein includes first and second spindle stocks 320 and 330 arranged oppositely to each other, and a tool rest 360 arranged between the two spindle stocks 320 and 330. On the first spindle stock 320, a first spindle 321 is rotatably supported. On the second spindle stock 330, a second spindle 331 is rotatably supported on the same axis as that of the first spindle 321. The tool rest 360 can be freely moved in a direction of a Z1 axis parallel to the axis of the first spindle 321, and in a direction of an X1 axis orthogonal to the Z1 axis. Further, the second spindle stock 330 can be freely moved in a direction of a Z2 axis parallel to the Z1 axis.
On a turret plate 361 of the tool rest 360, drills T1′ and T3′ are attached back to back to the same tool attaching position (station) 362. The first spindle 321 grips a work W1, and the second spindle 331 grips a work W2.
To machine the work W1 gripped by the first spindle 321 with the drill T1′, as shown in FIG. 16(a), the tool rest 360 is moved in the direction of the X1 axis so as to match an axis of the drill T1′ with the axis of the spindle 321. Then, as shown in FIG. 16(b), the tool rest 360 is moved in a direction of a −Z1 axis to feed the drill T1′ to the work W1. To machine the work W2 gripped by the second spindle 331 with the drill T3′, the tool rest 360 is moved in a direction of a +Z1 axis while a position of the X1 axis direction of the tool rest 360 is maintained.
In the NC lathe shown in FIGS. 16(a) to 16(c), the second spindle stock 330 is movable in a direction of a Z2 axis. Thus, instead of moving the tool rest 360 in the direction of the +Z1 axis in machining of the work 2, as shown in FIG. 16(c), the second spindle stock 330 may be moved in a direction of a −Z2 axis to machine the work W2 by the drill T3′.
In addition, in the NC lathe described in the Japanese Patent referenced herein, the movement of the second spindle stock 330 can be superposed on the movement of the tool rest 360 in the direction of the Z1 axis. Thus, drilling of the work W2 can be carried out by the drill T3′ while the work W1 is drilled by the drill T1′.
However, a drawback is inherent in the NC lathe shown in FIGS. 16(a) to 16(c), i.e., impossibility of off-line setting-up of tools T1 and T2 because the tools T1′ and T2′ are directly attached to the turret plate 361.
To prevent such inconvenience, a tool holder has been well-known, for example one similar to that shown in FIG. 17, which can attach two different tools.
As shown in FIG. 17, a tool holder 400 includes a holder body 401 attached to the turret plate 361 of the tool rest 360 of the NC lathe, a first tool attaching portion 410 for attaching the first tool T1′ such as a drill, and a second tool attaching portion 420 for attaching the second tool T2′ such as a turning tool, back to back with the first tool T1′.
The first tool T1′ is attached to the first tool attaching portion 410 by a bolt 440, and the second tool T2′ to the second tool attaching portion 420 by a bolt 450.
Each of FIGS. 18(a) and 18(b) shows a method of machining the works W1 and W2 by the tool holder 400, and the tools T1′ and T2′ attached to the tool holder 400. In FIGS. 18(a) and 18(b), portions similar to those of the NC lathe shown in FIGS. 16(a) to 16(c) are denoted by similar reference numerals, and detailed description thereof will be omitted.
In the machining example of each of FIGS. 18(a) and 18(b), the tool T1′ is positioned on an axis of the work W1 by the movement of the tool rest 360 in the directions of the X1 and Z1 axis. Then, by feeding the tool rest 360 in the direction of the −Z1 axis, the work W1 is machined by the tool T1′.
After the machining of the work W1 by the tool T1′, the tool rest 360 is moved in the directions of the +X1 and +Z1 axis, and a edge of the tool T2′ as a turning tool is pressed to an outer peripheral surface of the work W2 of the second spindle 331. Then, by moving the tool reset 360 in the direction of the Z1 axis or the second spindle stock 330 in the direction of the −Z2 axis, the tool T2′ is fed to the work W2, and machining is carried out.
FIG. 19 shows another embodiment of the tool holder shown in FIG. 17.
A tool holder 450 of FIG. 19 includes a tool body 451 attached to a peripheral surface of the turret plate 361 of the tool rest 360, and two tool attaching portions 452 and 453 formed from the tool body 451 in a diameter direction of the turret plate.
In this example, tools T4′ and T5′ as turning tools are attached to the tool attaching portions 452 and 453 with edges thereof shifted in position from each other.
Sizes of the tool attaching portions 452 and 453 are predetermined according to shapes of machined portions W1a and W2a of the works W1 and W2 such that edge positions of the tools T1 and T2 can be shifted by a predetermined amount (H in the example of FIG. 19).
In a machine tool shown in FIG. 19, a first spindle stock 320′ can be freely moved in a direction of a Z0 axis, and a second spindle stock 330 in a direction of a Z2 axis. Also, the tool rest 360 can be freely moved in a direction of an X1 axis.
The first and second spindle stocks 320′ and 330 are moved from both sides of the tool rest 360 to the tool rest 360 side, and the tool rest 360 is moved in the direction of the X1 axis. Accordingly, the works W1 and W2 are machined by the tools T1 and T2.
Use of the tool holder 450 capable of attaching the tools T1′ and T2′ with their knife point positions shifted from each other according to the shapes of the machined portions W1a and W2a enables the works W1 and W2 to be simultaneously machined even in the conventional NC lathe.
Thus, it is well known that a plurality of machining operations carried out for a plurality of works without any adjustment of the tool rest by attaching two or more tools to the tool holder, and execution of such machining on the tool rest by the tool holder having a pair of tools contribute to shortening of machining time, and a lower price of the machine tool.
However, problems have been inherent in the above-described tool holder. Namely, because of the integral formation of the tool attaching portions for attaching the tools with the holder body, in addition to the combination of the drills and the turning tools shown in FIG. 17, a tool holder must be prepared for each combination of tools such as a combination of drills, or a combination of turning tools. Also, in the tool holder 450 shown in FIG. 19, a number of tool holders 450 having predetermined sizes of tool attaching portions 452 and 453 must be prepared according to the shapes of the machined portions W1a and W2a of the works W1 and W2.
In addition, in recent years, there has been an increase in demand for a compact and low-priced machine tool capable of machining a work more efficiently and at lower costs.
Furthermore, in a production system and production facilities including machine tools, shortening of setting-up time including changing of tools for work machining, a reduction of types of tools including a tool holder, a reduction of storage space thereby needed, and a reduction of running costs including an increase of storage efficiency or the like are essential. There has also been an increase in demand for these matters.
The present invention has been developed to solve the foregoing problems and meet the demands. Objects of the invention are to provide a tool holder capable of having not only similar but also different types of tools easily attached thereto detachably, and easily adjusting the tools attached to the tool holder in a positional relation suitable for work machining, and a work machining method capable of efficiency machining a work by using this tool holder. More particularly, the invention provides a tool holder capable of carrying out machining by a compact and low-price machine tool when a plurality of works are simultaneously machined by a plurality of tools, and a work machining method using this tool holder.